Sedimentation tanks have a vital role in the overall efficiency of solid particles removal in treatment units. Therefore, an in-depth study these tanks is necessary to ensure high quality of water and increasing the system efficiency. In this work, an experimental rectangular sedimentation tank has been operated with and without a baffle to investigate the system behaviour and effectiveness for the reduction of solid particles. Turbid water was prepared using clay, which was collected from the water treatment plant of Al Maqal Port (Iraq), mixed with clear water in a plastic supply tank. Raw and outflow samples were tested against turbidity after plotting a calibration curve between inflow suspended solids versus their corresponding turbidity values. The key objective was to assess the impact of different flow rates, particle concentrations, heights and positions of the baffle on the system efficiency. Findings showed that the tank performance was enhanced significantly (p < 0.05) with the use of a baffle placed at a distance of 0.15 of tank length with height equal to 0.2 of tank depth. Higher removal efficiency (91%) was recorded at a lower flow rate (0.015 dm3∙s–1) and higher concentration (1250 mg∙dm–3), as the treatment efficiency enhanced by 34% compared with the operation without a baffle. Placing the baffle in the middle of the sedimentation tank produced the worst results. System efficiency for solids removal reduced with increasing baffle height. Further research is required to evaluate the efficiency of an inclined baffle.